Several internal combustion engines have a layout where multiple camshafts each have intake and exhaust cams along their length. Examples of such a layout can be found in the following engines:                Push rod V-engines, where two parallel camshafts are situated next to each other in the engine block. Several V-twin motorcycle engines currently use such a layout.        DOHC (dual overhead cam) engines where the valve layout is rotated by 90° (to improve port generated swirl). Each camshafts then has intake and exhaust cams along its length.        SOHC. (single overhead cam) V-engines where a single camshafts controls all the valves on each bank.        
It is desirable to be able to control the phase of the intake and the exhaust cams in such engines independently and this would be rendered possible by the use of two SCP camshafts. However, the use in such a case of two independent actuators (or phasers) to transmit torque separately from the engine crankshaft to each SCP camshafts would present problems. In particular, such a solution would prove costly to implement, because a separate set of sensors, control valves, oil feeds, and actuator parts would be required for each camshafts. There would also be added complications for the electronic engine control unit.